1. Field of the Invention
This invention relates in general to filters for the air handling and treatment systems of automotive vehicles and, more particularly, to a filter assembly including means for moving the filter out of the flow path of the air handling system when the filter is blocked.
2. Description of the Prior Art
The air treatment and handling system of a modern automobile customarily comprises air intake means for drawing air from within the vehicle's passenger compartment as well as fresh outside air through the firewall of the vehicle and into a plenum located on the engine side of the firewall. The air is then moved through the plenum by means of a centrifugal blower which delivers the air to a chamber containing an air conditioning evaporator coil. From there, the treated air passes back through the firewall and into a distribution system carried under the dashboard of the vehicle.
It is desirable, because of the large amount of air pollution in urban environments, to provide some type of filter for removing dirt particles and other contaminants which enter the aforementioned type of air treatment and handling system. However, conventional filter elements, which merely consist of stationary screens, strainers and in some cases more exotic materials, positioned across the flow passage of the air handling system, suffer from the drawback that they tend to become clogged rather quickly, thus preventing the air from traveling through the system, and severely decreasing the efficiency of the system. When clogging occurs, the filter must be replaced or removed for cleaning. Due to the complexity and compact configurations of todays automotive air treatment and handling systems, the entire blower motor assembly and/or the instrument panel of the vehicle would need to be disassembled in order to gain access to the filter area in the absence of a unique filter and mounting arrangement. This, of course would require considerably more time and labor than the average vehicle owner would be willing to expend for a simple filter.
Several attempts have been made in the past to devise automotive air handling systems having replaceable air filters. Such attempts have been described in U.S. Pat. No. 2,203,477 to Wahlberg, U.S. Pat. No. 2,213,017 to Perkins, U.S. Pat. No. 4,610,703 to Kowalczyk, and U.S. Pat. No. 4,629,479 to Cantoni. The filter assemblies of both Wahlberg and Perkins, however, were designed for vehicle styles of the 1930's and 1940's, and simply would not fit in the more complex and compact systems of modern automobiles. The inventions of both Kowalczyk and Cantoni relate to removable filter elements for the air handling systems of modern automobiles, together with means for sensing when the filter is clogged. In the Kowalczyk patent, the sensing means is associated with indicating means such as a warning light for notifying the vehicle operator that the filter needs to be changed. In the Cantoni patent, the sensing means is associated with means for stopping the fan which circulates air through the system, and thus prevents the system from operating until the clogged filter is replaced with a clean one. In both of these cases, however, access to the filter elements is blocked by obstructions such as the blower motor, fan, evaporator coil and the like, so the process of replacing the filter is as laborious as ever. Furthermore, both the Kowalczyk and the Cantoni devices lack any type of bypass means for allowing air to blow through the system after clogging is detected. Thus, the vehicle owner is forced to put up with an inefficient or inoperative air handling system until he or she has time to buy a new filter, which may be extremely inconvenient if the owner is busy or if the correct filter is unavailable.
Other patents of interest are U.S. Patent No. 1,914,667 to Kolls, which describes a filter arrangement for a furnace, U.S. Pat. No. 2,074,152 to Mueller, which describes a filter arrangement for a household conditioning system, U.S. Pat. No. 2,811,840 to Thompson, directed to a filter for a refrigerator, and U.S. Pat. No. 4,195,383 to Leinfelt which describes a filter for a vacuum cleaner. The devices of Kolla, Mueller, and Thompson all comprise pivotably mounted filter elements which act essentially as flap valves allowing air to continue through the system even after the filters are clogged. None of these devices can be satisfactorily adapted to automotive air handling systems, however, because the crowded, compact arrangement of elements in a modern vehicle simply does not allow enough room for a pivoting type filter. The patent of Leinfelt is directed to a diaphragm-actuated means for detecting and indicating when a filter is clogged, but does not include any type of filter bypass means, and is silent as to how the filter is removed and/or replaced.
Therefore, a need exists for a new and improved filter for an automotive air handling system which overcomes some of the problems and shortcomings of the prior art.